Blue tits: passerines seen from the peripheries (part II)

Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! Follow on Twitter @TetZoo.

Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! Follow on Twitter @TetZoo.

Preening Eurasian blue tit doing weird stuff with its wing: a bird that I photographed in April 2014. Photo by Darren Naish.

Today I want to talk more about passerines, and I know that this will make you happy. In particular: TITS!! Tits of several species are ubiquitous here in Europe. The two that are most frequently encountered here in southern England are the Great tit Parus major and Eurasian blue tit Cynanistes caeruleus. This article was originally about both species but it became over-long so I’ve ended up splitting it in two.

Oh yeah: again, the ‘from the peripheries’ idea alluded to in the title relates to the fact that western Europe has to be considered a far-flung outpost of the Passerine Empire (see the previous article for clarification). Read on for more about that.

The best place to go when wanting to find out about the tits of the world.

But, as more data has come in, people have become increasingly unhappy with the idea that the species concerned should really be lumped into the one mega-genus, and the idea that those ‘subgenera’ should be stand-alone ‘genera’ has become popular (Gill et al. 2005, Gosler & Clement 2007, Johansson et al. 2013)… albeit not universally accepted among specialists (Päckert & Martens 2008). Decisions like this are always subjective, to a degree. However, in this particular case justification for the idea comes from the fact that morphologically aberrant tits that – in traditional taxonomy – would definitely warrant their own ‘genera’ are known to be deeply nested within ‘Parus’ of tradition. I’m referring to Pseudopodoces humilis, the Tibetan groundpecker: a tit so weird that it was long misclassified as a small ground-jay (and known as the Tibetan ground-jay). Not only is it a member of Paridae, it’s especially close to the Great tit and its relatives, the definitive Parus tits (James et al. 2003) (this has been covered briefly on Tet Zoo before: see links below).

Eurasian blue tit in typical foraging pose. Photo by Darren Naish.

The way the tit family is distributed indicates that eastern and tropical Asia was the main centre of its diversification, with molecular clock data suggesting that most divergences within Paridae happened in Asia during the Middle Miocene (Päckert et al. 2007, see also Johansson et al. 2013). At least two crossings into North America occurred during the Pliocene or Late Miocene; movements west into Europe and Africa happened at about the same time (Gill et al. 2005, Päckert et al. 2007). The taxa that belong to the blue tit complex (see below) diversified during the Pliocene, with the Mediterranean region being the apparent ‘centre’ of their evolution (Päckert et al. 2007). Again, western Europe is a ‘fringe’ region in biogeographical terms – but an important one for migrants that breed further south or east given the ridiculous amount of daylight it receives in summer.

Anyway, we’re here to talk specifically about the Eurasian blue tit. This is a small, garden-frequenting, woodland-dwelling tit, typically about 12 cm long and 11 g, and generally short-tailed and with a unique combination of black horizontal eyestripe, white cheek patches, blue crown and yellow breast. The sexes look similar but with practise you can distinguish the duller-blue females from the brighter males. It can occur at very high densities when conditions are right (as in, two pairs per hectare) and produces one of the largest clutches of any passerine: 7-12 eggs per clutch are about average, and 15 or 16 eggs are not uncommon. The record number is 22.

Blue tits of all sorts are typically insectivorous predators that eat huge numbers of caterpillars, aphids, micromoths and other small insects. They also eat seeds and buds, but I’m especially interested in the fact that they also seemingly serve an important role as pollinators. If you watch them often enough, you’ll see them reaching into flowers and emerging with pollen stuck to their faces. However, visiting flowers (and foraging from, or within, them) isn’t the same thing as pollinating them, and the apparent role of Eurasian blue tits as pollinators (especifically of introduced Fritillaria imperialis lilies planted in England) wasn’t brought to attention until 1985 (Ford 1985).

Blue tits are probably only part of a suite of Old World passerines that visit flowers to rob nectar: leaf warblers (discussed in the previous Tet Zoo passerine article) are among the others. What’s fascinating from a historical, evolutionary perspective is the suggestion that some of these birds might originally have been ‘flower-birds’ that formerly took advantage of specialised European plants that became extinct following the Pleistocene glaciations (Búrquez 1989). In the European region, such so-called ornithophilous plants are only present today on the Canary Islands. This puts a new spin on the idea – previously discussed in my article about the ‘ghosts’ of extinct birds – that ornithophilous plants present across Eurasia might indicate co-evolution with extinct hummingbirds, since it could mean that ornithophilous flowers co-evolved with known, extant Eurasian taxa like leaf warblers, not with hypothesised extinct hummingbirds.

Blue tit visiting flower blossum, presumably for nectar. Note the pollen stuck to the feathering close to the base of its bill. Photo by Darren Naish.

As is so often the case with widespread passerines, the Eurasian blue tit is polytypic – that is, there are several different forms, traditionally regarded as ‘subspecies’. A set of taxa that occur across northern Africa and on the different Canary Islands have conventionally been regarded as C. caeruleus ‘subspecies’ but they’re increasingly regarded as belonging to a distinct species: the African blue tit C. teneriffae. Furthermore, there are suggestions that C. teneriffae is a species complex and that further splitting is needed. Much debate has ensued (e.g., Kvist 2006, Sangster 2005, Kvist et al. 2005). I’m lucky enough to have seen African blue tits on several occasions – much as I’d like to talk about them right now, it’ll have to wait to another time. I never planned to write this much about blue tits in the first place anyway, gah! Until next time…

About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! Follow on Twitter @TetZoo.

The biggest of the world’s 57 or so tits is the tropical Asian Sultan tit Melanochlora sultanea – a really interesting black and yellow species. The biggest individuals can be 20 cm long and weigh as much as 49 g (for comparison, chickadees and blue tits are about 10-14 g). This size goes for the nominate Sultan tit ‘subspecies’ – the others are smaller.

Nah, I’m just grumpy that no fewer than three of the authors I generally follow (Naish, Stross, and Scalzi) are going to LonCon right now, and I can’t be there to bug them. Such is life. Perhaps we should hang this thread at 22 for a while, just to mess with Darren?

Interesting non-sequitur is that Ol’ Google seems to think that Tit the bird is of Scandinavian derivation from an old word for sparrow, while tit from teat is Old English. So we’ve got a pair of etymological false friends here apparently. Of course, if we wanted to be politically correct, we’d pick an australasian term for these birds instead, and stop calling them tits entirely.

Having seen two of the Canary Island blue tits recently they seem to have rather different habitats than the European mainland species. On Tenerife I saw them in pine forest, though I expect they occur all over the island, but on Fuerteventura they were feeding in a palm tree, which looked rather odd. The Fuerteventura birds apparently respond to play back of African Blue Tit calls, but the birds on the other islands do not, and they are fairly distinct genetically. I gather that the Dutch Birding Association has them listed as separate species, which seems logical. A lot of other Canarian “subspecies” belong in the same category as well – the European Robins on Tenerife and Gran Canaria are probably full species (and may be distinct from each other as well).

Pseudopodoces is one of several bird species that have in the past decade or so moved from one passerine superfamily to another. How many others can you name? And are there any good examples outside passerines?

Some other passerines that have jumped superfamilies:
- Kakamega has been mentioned, but the other “arcanatorids” (an African clade of very basal passeroids) have in the past been placed in Turdidae s.l.
- Paramythiid berrypeckers, from Passeroidea to Corvoidea
- Chelidorhynx hypoxantha, from Rhipidura (Corvoidea) to Stenostiridae
- Leonardina, from Timaliidae (Sylvioidea) to Muscicapidae
- Elachura, from Timaliidae to a “superfamily-level” group of its own
- Notiomystis (the hihi) from Meliphagidae to sister of Callaeatidae, in an unresolved position with Corvoidea and Passerida
- Mohoidae (extinct Hawaiian “honeyeaters”), from Meliphagidae to Bombycillodea
- Hylocitrea, from Pachycephalidae to Bombycilloidea
Outside of passerines: Pluvianus (from Lari to Charadrii) is the only example I could think of at the moment.

John Harshman: Sibley & Ahlquist actually mentioned a morphological character distinguishing “Corvida” from Passerida: the single vs. double pneumatic fossa of the humerus. I don’t know if there are exceptions. But for how many of the birds I listed here have any anatomical studies been done?

Dartian: I actually thought of those after writing my comment, but they just moved to another family, not superfamily. However, the reason for this is only that passerines are split much more than galliforms, I think the divergence times here are similar to those of some passerine superfamilies. Which again demonstrates how subjective ranks are.
Oh, and within passerines I forgot the Malagasy “babblers” Newtonia and Mystacornis that turned out to be vangas (Corvoidea). And Hypocryptadius (the Cinnamon Ibon, from the Philippines), which moved from white-eyes (Sylvioidea) to being an insectivorous old world sparrow. In general, many species mentioned here were formerly classified as babblers (Timaliidae), which always was a wastebasket family. Ernst Hartert rhymed in the 1920s: “Was man nicht unterbringen kann, sieht man als Timalien an” (What one cannot classify, one regards as babblers), and this essentially didn’t change until molecular studies were done.

Those famously undefinable old school babblers having been mentioned, note that *Picathartes* and *Eupetes* used to be babblers at one time and are now, together with *Chaetops* from the former Muscicapoidea in their own superfamily Picathartoidea, and probably are basal Passerida.

There’s also the shrike-babblers jumping ship from the babblers to the vireos, deep in Corvida.

John Harshman: Sibley & Ahlquist actually mentioned a morphological character distinguishing “Corvida” from Passerida: the single vs. double pneumatic fossa of the humerus. I don’t know if there are exceptions. But for how many of the birds I listed here have any anatomical studies been done?

Yes, I thought about mentioning that. A great many taxon assignments have been based on superficial anatomy of plumage, bill shape, and such. Looking at osteological and other internal anatomical characters in detail can often help, but there are so damn many passerines. However, returning to Paridae for a change, Pseudopodoces is a great example, as Helen James was able to place it in Paridae using osteological characters.

Thanks for all the fine examples of superfamily-switching. This is one reason I try to avoid passerines as much as possible.

New Zealand wrens are really very old. Supposedly they’ve been distinct since the late Palaeocene, and really diverge from the rest of the passerines very early in the passerine radiation. This information is from brief googling, so should be taken with a pinch of salt.

Suffice to say, that must have been a weird time (the late Paleocene) in the southern continents, with australia getting colonised by the australidelpha (presumably via antarctica), sloths and phorusrachids getting going in antarctica, plus whatever the hell the St. Bathan’s mammal lineage doing…whatever it was doing.

Seeing as the rifleman, the commonest of the New Zealand wrens (and one of only two species, these days), goes by the generic name of Acanthisitta, it doesn’t surprise me that it would be compared to a nuthatch (Sitta). I believe it does show the same sort of bark-gleaning behaviour as nuthatches.

Christopher:
“as the rifleman [...] goes by the generic name of Acanthisitta, it doesn’t surprise me that it would be compared to a nuthatch (Sitta). I believe it does show the same sort of bark-gleaning behaviour as nuthatches.”

Hmm, good points about the rifleman’s behaviour; maybe its historical association with nuthatches wasn’t so totally off after all. (And the fact that it was indeed named ‘Acanthisitta‘ should have made that even clearer, but I failed to make that association.)